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Estimation of leaf and canopy photosynthesis of pot chrysanthemum and its implication on intensive canopy management

Weerakkody, W.A.P., Suriyagoda, L.D.B.
Scientia horticulturae 2015 v.192 pp. 237-243
Chrysanthemum, canopy, carbon dioxide, carbon dioxide enrichment, leaf area, leaves, lighting, models, photosynthesis, photosynthetically active radiation, temperature
Variation in leaf net photosynthetic rate (A) with the changes in incoming radiation at each leaf of pot chrysanthemum under different leaf temperatures (T1) were used to model the canopy net photosynthesis. Model parameterisation when A was Rubisco-limited, RuBp-limited, and triose-phosphate-utilization limited was made under constant or variable levels of intercellular partial pressure of CO2, photosynthetically active radiation (PAR; Q) and T1. The minimum A obtained from above approaches were considered as the estimate of A through the biochemical model and the A/Q responses developed were in close agreement with the measured A/Q responses at different Tl. Top, middle and bottom leaf area with 23%, 48% and 29% of the leaf area of a plant contributed 30–32%, 47–51% and 18–20% of the canopy photosynthesis, respectively. The peak rate of net photosynthesis was reached when CO2 enriched to 1000ppm, PAR at 1000–1400μmolm−2s−1 and Tl at 20 and 28.8°C. Therefore, artificial lighting alone at lower temperatures is not adequate to achieve a higher canopy photosynthesis in pot chrysanthemum as lower leaf layers are not contributing to A and combination of CO2 enrichment with artificial lighting at higher temperatures are required to achieve the maximum production.